Method of grinding



Aug- 11, 1931- A. L. NELsoN 1,818,084

OOOOOOOOOOOOOO NG P'atentecl Aug. 11, 1.931

UNITED STATES PATENT OFFICE .ADOLPH I. NE LSON', F DETROIT, MICHIGAN, ASSIGNOR TO BOHN ALUMINU M &; :BRASSf CORPORATION, 0F DETROIT, MICHIG-AN ME'rHoD or GRINDING Application filed May 3, 1928. Serial No. 274,716.

This invention relates to a method of grinding hollow articles, such as pistons.

The object of the invention is to produce a piston in which the exterior diameter of the lower end of the piston will be slightly smaller on one diameter than on a diameter at right angles thereto. The smaller diameter is preferably made to coincide with the axis of the piston pin bosses.

This object is attained by providing during the grinding operation a less firm support 'for the skirt wall at the parts that are to lie on the major axis of the skirt, thereby permitting these parts to spring inwardly and therefore lose less material during grinding. v

While preferred methods of carrying out the process have been disclosed herein, it will be clear that the process may be modified without departing from the spirit and scope V`of the invention as hereinafter set forth and claimed.

In the drawings:

Fig. 1 is an elevation of apparatus adapted carry out the invention.

Fig. 2 is a fragmentary detail of the mechanism of Fig. 1.

YFig. 3 is a section on line 3-3 of Fig. 1.

Fig. 4. is a view similar to Fig. 3 but illus- 930 trating a modification of the process.

3/ In producing pistons for internal combusi tion engines it is at times advisable to give the exterior of the open end of the piston a slightly oval shape, so that the external diameter of the skirt on the axis of the piston pin bosses and lying below said bosses, is slightly smaller than the diameter at right angles thereto. The present invention provides a simple and efficient process for giving the piston this shape when it is desired.

Referring to the drawings more particularly, the reference numeral 10 indicates the table of a grinding machine, the driving center 11 being journaled in a bracket 12 and rotated by any suitable means such as pulley 13. The opposite center 14 is journaled in the upper end of bracket 15 and is pressed toward the center 11 by an internal spring, not shown. A driving pin 16 projects from 'driving lcenter 11 and is adaptedl to engage and properly position the work.

The piston comprises a head 17, and a skirt 18, and is formed with piston pin bosses 19 on opposite sides of the skirt. The driving 'center 11 is cut away for small sectors on opposite sides as indicated at 20 and 21 on Fig. 3, and the piston is placed on the center in such a position that the cut-outs 20 and 21 lie on an axis .A -A, which is at right angles to the axis of the pin bosses. The driving ,pin 16 engages a part of thepiston to maintain the piston and driving center in this relation during grinding.

The grinding operation is'now carried out with the usual grinding tool, and it will be evident that as the tool is pressed against 'the periphery of the skirt the parts of the skirt adjacent the ends of axis A-A will give ini wardly, vand hence less material will be removed from these parts than from the parts that are solidly supported by the center 11. After the exterior of the piston has been ground to the desired extent it is removed from the grinding machine, and it will be found that the lower end of the skirt has a greater diameter on axis A-A than on the axis parallel to the axis of the pin bosses.

Fig. 4 illustrates a difierent method of pro-- ducing a similar result. In this case the driving center 22 is of completely circular shape, and the support of the piston skirt is provded by ribs 23 projecting inwardly at the lower end of the skirt. These ribs extend along the skirt on the sides below the pin bosses but are discontinued for a distance about each end of axis A--A.

VVith this construction the parts of the skrt below the pin bosses are firmly supported. by the engagement of the ribs 23 with the drving center 22, while the parts of the skirt adjacent the ends* of axis A-A have no po'stive support. And in this way the grndmg' tool will remove more material from the walls below the pin bosses than from the parts lying at the ends of axis A A. producing a finished piston which is nav. rower on the diameter Yparallel to the pin bosses at the lower end of the skirt than on the diameter ofaxis A-A.

I claim: I 1. The method of finishing a hollow, cylinvdrical article Which comprises supporting the interior of an open end in such a Way as to support the wall of the article more firmly along one diameter of the article than along a second diameter at right angles to the first diameter, and then grinding the exterior of the article.

2. The method of finisliing a hollow, cylindrical article having a closed end, which comprises holding a true center on the closed end, supporting the interior of the open end in such a Way as to support the wall of the article inore firmly along one diameter of the article than along a second diameter at right angles to the first diameter, and then grinding the, exterior of the article.

3. rl`he method of finishing a piston having a closed head and pin bosses, Which comprises holding a true center on the closed end, supporting the interior of the open end in such a way asto support the wall of the piston more firmly along adiameter parallel to the axis of the pin hosses than along a diameter at right angles to the aXis of the pin besses, and then grinding the exterior of the article.

ll. The method of finishing a piston having a closed head and pin besses, Which comprises holding a true center on the closed end, supporting the opcn'cnd With a member Which eugages the piston at points below the pin besses but which does not engage the piston at points along` a diameter at right angles to the axis of the pin bosses, and then grinding the exterior of the piston.

K rlllm paul-11051 (x-F Rnicling a lanllnw nvlindrical article Which comprises supporting the interior of an open end in such a Way as to support the Wall of the article more firmly along one diameter of the article than along a second diameter at an angle to the first diameter, and then grinding the exterior of the article.

In testimony Whereof lt afix my signature.

ADLPH L. NELSN.

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